The present invention relates to vibration plates for music box movements, and more particularly, to vibration plates having fifty to seventy vibration reeds for high-grade music box movements.
In a conventional vibration plate for music box movements, a number of vibrating reeds are arranged in the form of comb teeth of equal width. In a high-grade music box having a large number of reeds and capable of playing two or more music selections, in general, the reeds except for the lowest frequency reed are all equal in width to one another, and the end portion of each reed is tapered. Only the lowest frequency reed is made larger in width than the other reeds to provide for it a greater vibration energy.
In general, the vibration plate is divided roughly into three regions: a high frequency region, a middle frequency region, and a low frequency region.
In one example of a conventional vibration plate, as shown in FIG. 1 and FIG. 3B, each of reeds 5 includes a base portion 51, a sloped portion 52, and an end portion 53. In the greater part of the reeds 5, the sloped portion 52 forms an angle of 45.degree. (a') with the longitudinal axis of the reed, and the sloped surfaces are about 1 mm in length. In the remaining 14 to 15 reeds 5, namely, those for higher frequencies, the sloped surfaces are about 4 mm in length. The vibration plate has mounting holes formed at equal intervals which are used to secure the vibration plate to the movement's frame with screws.
As shown in FIG. 2, a seat 57 is welded to the base part 54 of the vibration plate 4, which has a thickness of T'. Each of the reeds 5 extends from the base part and has a thin middle part 55 and a weight part 56. In the reeds for lower frequencies, the weight parts 56 are augmented, while on the other hand, in the reeds for high frequencies, the weight parts 56 are made thinner.
In a music box movement having a vibration plate 4 thus constructed,
(1) the tonal range is small, and therefore the music selections employable are limited,
(2) the tonal quality is not sufficiently high for a high-grade music box,
(3) tones in the middle frequency range are unsatisfactory, being rather uncrispt and having insufficient reverberation,
(4) the volume of sound in the high frequency range is not well balanced with that in the low frequency range, and
(5) during assembly, a welding operation must be additionally performed, requiring much labor and time.
Therefore, in order to provide a high-grade music box movement, it is necessary to eliminate the above-described difficulties accompanying the conventional vibration plate.